Abstract Class

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The class which can not be instantiated is known as an Abstract Class. This particular article contains the details of an Abstract Class.

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The class which cannot be instantiated is known as an Abstract Class. That is, an object of it cannot be created. Hence it must be inherited. Let me cite some of the features of an Abstract Class.

Features of an Abstract Class

1. Abstract Class cannot be instantiated.
2. An Abstract Class must be inherited.
3. It may have Concrete Methods.
4. It may have Abstract Methods.
5. An Abstract Method of an Abstract Class must be overridden.
6. An Abstract Class can only contain Abstract Method.

Abstract Class cannot be instantiated.

Error Message

It must be inherited


Abstract Class may have Concrete Method


Abstract Class may have Abstract Method

Error Message

An abstract method of an abstract class must be overridden


An Abstract Method can be present only in Abstract Class

Error Message

Hope this article will be useful.

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About the Author

Full Name: Zinnia Sarkar
Member Level:
Member Status: Member
Member Since: 7/24/2010 12:50:40 PM
Country: India
Regards, Ganeshji

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Comments or Responses

Posted by: Madhu.b.rokkam on: 2/17/2011 | Points: 25
Good one .. :)
Posted by: Karthikanbarasan on: 2/17/2011 | Points: 25
Nice article for the beginers
Posted by: Tripati_tutu on: 2/17/2011 | Points: 25
I think this is good for new learners.
Posted by: Kishork80 on: 2/17/2011 | Points: 25
The statement in the last point 'An Abstract Class can only contain Abstract Method is ambiguous.'
What I say is ,
An abstract class can have a Normal method as well as an abstract methods.
That means If any one method inside a class is abstract the WHOLE CLASS has to be abstract but not vice versa.

Posted by: Ganeshji on: 2/17/2011 | Points: 25
Thnx Kishork80.
Posted by: Venu_msis on: 2/17/2011 | Points: 25
Nice Article!
Posted by: Karthikanbarasan on: 2/17/2011 | Points: 25
Can you post similarly for Interface, Encapsulation and Abstraction with examples? it will be really helpful.
Posted by: Ganeshji on: 2/17/2011 | Points: 25
Yes, Karthikanbarasan I have posted a similar article on Interface today. Rest i shall cover asap. Plz keep on suggesting me in this way. Many Thnx!
Posted by: Pradsir on: 2/17/2011 | Points: 25
Ganesh ji..

Thanks for Submitting very good articles..
I have got few quick Q ..

can we have seald methods in Abstract Class ?
can we have Virtual methods in Abstract Class ?


Posted by: Karthikanbarasan on: 2/17/2011 | Points: 25
Nice Ganeshji.... Its really helpful... Keep going....
Posted by: Bcs2002 on: 2/18/2011 | Points: 25
Good article. But when and where should you user abstract classes and what is the use of abstract classes?
Posted by: Kishork80 on: 2/18/2011 | Points: 25

We can not have 'Sealed' type because sealed contradicts the purpose of 'Abstract'. On the other side we can haev virtual because it can be overriden in the implemeting class.

See the code below.
abstract class TTest
public virtual void T1()
{ }
//ERROR:'ConsoleApplication2.TTest.T2()' cannot be sealed because it is not an override
public sealed void T2()
{ }

Posted by: Pradsir on: 2/18/2011 | Points: 25
@ KishorK80..

Thanks kishor..

But i think we need to check the below line of code.

using System;
class Program
static void Main(string[] args)
{ C c1 = new C();


class A
public virtual void Hello()
Console.WriteLine(" Say Hello");


abstract class B : A
public sealed override void Hello()
Console.WriteLine(" Say Hi");


class C : B

//Output is
// Say Hi
//Press any key to continue . . .

Here I was able to declare Sealed Method in Class B which is an abstract class.


Posted by: Pradsir on: 2/18/2011 | Points: 25

Abstract class can be used in order to create the looseley coupled environment.

We can put all common set of functionality & Behaviour in the abstact class..
& then we can derive the abstract class implementing abstract methods..

Posted by: Akiii on: 8/15/2011 | Points: 25
Very good explanation......
just can you tell me what is the sole purpose of an abstract class ?

Thanks and Regards
Posted by: Ganeshji on: 8/18/2011 | Points: 25
Yes Akii! Very Good Question u have. If anyone wishes to make use of a particular function signature, then abstract class can be ideally used.
Posted by: Kamlesh420 on: 12/20/2011 | Points: 25
nice and simple article thanks

can u also plz define interface
Posted by: Ganeshji on: 12/20/2011 | Points: 25
Thanks Kamlesh. I have an article on interface in the following link.http://www.dotnetfunda.com/articles/article1184-an-interface-in-csharp-.aspx. Enjoy Reading!
Posted by: Vijayakumarp on: 3/19/2012 | Points: 25
Nice one Zinnia Sarkar.. Thanks for Great explanation...
Posted by: Ganeshji on: 3/19/2012 | Points: 25
Thanks Vijayakumarp!

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